Dispensers which are adapted to deliver disinfecting or aesthetic ingredients to a toilet tank to condition water in the toilet tank and bowl are well known in the prior art, as are dispensers which are described hereinafter as "passive" in that they require no moving parts but deliver a disinfecting or aesthetic solution responsive to the flushing of a toilet at the usual intervals.
A patent application owned by the owners of the present application, Ser. No. 897,477, filed by Dirksing, on Apr. 18, 1978, (especially FIGS. 12-19 and the accompanying text) discloses an especially desirable toilet tank dispenser which receives water from a toilet tank in which it is immersed as the tank water rises after a previous flush, transmits this water to an internal receiver which is isolated by an air lock from the tank water when the toilet is full, contacts the water in the reservoir with a cake containing active ingredients such as hypochlorite to form a hydrochlorite solution, stores this hypochlorite solution in the reservoir, and releases this hypochlorite solution to the toilet tank water responsive to the lowering of the level of water in the toilet tank when the toilet is flushed. This hypochlorite dispensing system is well adapted to a consumer product which may be used to condition toilet tank and bowl water. The absence of any moving parts in the dispenser makes it possible to produce a dispenser very inexpensively, as by thermoforming two halves and sealing them together. Such a dispenser may be made so cheaply that it is well adapted for use as a disposable dispenser which may be discarded after the active ingredients sealed therein are depleted.
Two problems have been noted with prior art hypochlorite cakes which are adapted to be placed inside the reservoir of a toilet tank dispenser for the purpose described above. The first of these problems is that a compressed solid cake of material containing soluble hypochlorites tend to deliver a high level of available chlorine initially, so that much of the available chlorine is released in a relatively short time. The remaining available chlorine in then released much more slowly. Thus, prior art dispensers do not deliver a relatively consistent amount of available chlorine over a long period of time. The following references contain discussions of this problem in other arts: U.S. Pat. No. 3,154,495, issued to Robson et al. on Oct. 27, 1964; U.S. Pat. No. 3,036,013, issued to Jaszka et al., on May 22, 1962; U.S. Pat. No. 3,234,141, issued to Robson on Feb. 8, 1966; U.S. Pat. No. 2,023,459, issued to Bachman on Dec. 10, 1935. (It will be noted that none of the above references deals with hypochlorite containing compositions for use in a toilet tank.)
A second problem which has been noted for hypochlorite cakes used in connection with prior art passive dosing dispensers is the tendency for the pourable fluid capacity (as defined hereinafter) of the dispenser reservoir to increase as active ingredients in the solid cake are successively dissolved and removed from the dispenser during the life cycle of the product. As a result of this increase in pourable fluid capacity, a dispenser which has been in use for some time contains a relatively large mass of hypochlorite solution, compared to the quantity contained in the reservoir during the early part of the usage life of the dispenser. When the dispenser is subsequently placed in contact with organic material, such as by storing it in a wastepaper basket for future disposal, this mass of hypochlorite solution may escape from the dispenser, come into contact with the organic matter in the wastepaper basket and oxidize this organic matter while releasing chlorine gas to the atmosphere surrounding the wastepaper basket. This problem usually occurs when a dispenser is discarded prematurely, before its active ingredients have been depleted.
The instability of hypochlorite containing compositions, particularly those containing calcium hypochlorite, is generally known. See, for example, U.S. Pat. No. 3,793,216, issued to Dychdala on Feb. 19, 1974, and U.S. Pat. No. 3,560,396, issued to Robson on Feb. 2, 1971. The chlorine releasing reaction is believed to take place in three steps as follows: ##STR1##
It has been found that, when hypochlorite solutions from the preferred toilet tank dispensers are brought into contact with organic matter such as paper toweling, an appreciable quantity of chlorine gas is released and the reacting mass may heat up to nearly the boiling temperature of water. (An example of the reaction of hypochlorite solutions with paper toweling is given in one of the examples below.) The problem of reducing the release of chlorine and evolution of heat when a toilet tank dispenser is thrown away and brought into contact with organic matter is not dealt with in the prior art. Accordingly, it is an object of the present invention to reduce this problem by providing a hypochlorite cake composition which is adapted to act in conjunction with the dispenser to limit the quantity of available chlorine which the dispenser can release when it is discarded, and as a result placed in contact with organic matter.
Other objects of the present invention, although not limited by their enumeration, are to provide an alkaline composition in solution and to level the delivery of available chlorine over a long period of time, throughout a life cycle of many flushes.